The present invention relates in general to the art of earth boring and, more particularly, to a downhole drilling motor that is carried near the end of a rotary drill string and actuated by the down-flowing drilling mud thereby driving a rotary drill bit for the drilling of oil and gas wells and the like.
The conventional U.S. system of oil well drilling involves the rotation of the string of drill pipe with a rotary drill bit located at the end of the drill string. During drilling, mud is pumped downward through the drill string to remove the material loosened by the drill bit. A drilling system that is also known involves the use of a downhole drilling motor powered by the circulating drilling mud. Downhole motors presently in use or potentially usable are electric or fluid (turbine, Moineau, and vane type) motors. The downhole motor operates in a fluid-laden borehole and the atmosphere of highly abrasive fluid stands in the way of any normal lubrication of the wear parts. Its limited diameter limits the internal design beyond that possible with motors used above ground. When fluid-lubricated bearings are employed abrasive contaminants in the drilling fluid will be circulated through the bearings and cause excessive wear and premature bearing failure. The present invention provides means to divert these abrasive contaminants through the shaft bore, along with the majority of the drilling fluid flow.